Controller for rotary electric machine apparatus

ABSTRACT

To provide a controller for rotary electric machine apparatus which can calculate the voltage command value of the converter which reduces power loss with good accuracy, in the case where the normal modulation control and the overmodulation control are switched and performed. A controller for rotary electric machine apparatus sets a system voltage that power loss becomes the minimum as the converter voltage command value, based on a power loss characteristics of the normal modulation control which is a power loss characteristics of at least the inverter with respect to the system voltage in performing the normal modulation control, and a power loss characteristics of the overmodulation control which is a power loss characteristics of at least the inverter with respect to the system voltage in performing the overmodulation control.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2020-00641 filed onJan. 7, 2020 including its specification, claims and drawings, isincorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to a controller for rotary electricmachine apparatus.

With regard to the above controller for rotary electric machineapparatus, the technology described in JP 5652549 B is already known. JP5652549 B discloses the rotary electric machine that the output voltageof the converter is shared with a plurality of inverters, and aplurality of rotary electric machines are controlled. In the technologyof JP 5652549 B, about each of a plurality of candidates of the voltagecommand value of the converter, the power loss of the DC power source,the power loss of the converter, the power losses of the plurality ofinverters, and these sum total power loss are calculated; a voltage atwhich the sum total power loss becomes the minimum is searched from theplurality of candidate voltages; and the searched voltage is set as thevoltage command value of the converter. In the technology of a JP5652549 B, the map data of each power loss in which the direct currentvoltage, the rotational angle speed of the rotary electric machine, thetorque, and the like are set as the arguments is memorized, and eachpower lose is calculated using the map data.

SUMMARY

However, in the technology of JP 5652549 B, without distinguishing eachpower loss characteristics of the normal modulation control in whichamplitudes of the three-phase voltage command values become less than orequal to the half value of the system voltage and the overmodulationcontrol in which the amplitudes of the three-phase voltage commandvalues exceed the half value of the system voltage, both arecollectively set as the PMW control mode. Then, in the technology of JP5652549 B, the power loss characteristics of each of the PWM controlmode and the rectangular wave PWM control mode is approximated by thequadratic function with respect to the system voltage.

However, between the power loss characteristics of the normal modulationcontrol, and the power loss characteristics of the overmodulationcontrol, the trends of characteristics are largely different. Therefore,if both are collectively approximated like JP 5652549 B, the approximateerror becomes large, and there is a possibility that the calculationaccuracy of the system voltage which makes power loss of the wholesystem the minimum may be deteriorated.

Thus, in the case where the normal modulation control and theovermodulation control are switched and performed, it is desired toprovide a controller for rotary electric machine apparatus which cancalculate the voltage command value of the converter which reduces powerloss with good accuracy.

A controller for rotary electric machine apparatus according to thepresent disclosure that controls a rotary electric machine apparatuswhich is provided with a rotary electric machine which has plural-phasewindings, a converter which can raise a power source voltage of a directcurrent power source to output to a system voltage line, and an inverterwhich is provided between the converter and the rotary electric machineand performs power conversion between the direct current power of thesystem voltage line and alternating current power which drives therotary electric machine, the controller for rotary electric machineapparatus including:

a converter voltage command calculation unit that calculates a convertervoltage command value within a range of greater than or equal to thepower source voltage and less than or equal to an output upper limitvoltage of the converter,

a converter control unit that controls the converter so that a systemvoltage which is a direct current voltage of the system voltage lineapproaches the converter voltage command value, and

an inverter control unit that calculates plural-phase voltage commandvalues, and controls the inverter based on the plural-phase voltagecommand values to apply voltages to the plural-phase windings,

wherein the inverter control unit switches and performs a normalmodulation control in which amplitudes of the plural-phase voltagecommand values become less than or equal to a half value of the systemvoltage, and an overmodulation control in which the amplitudes of theplural-phase voltage command values exceed the half value of the systemvoltage, and

wherein the converter voltage command calculation unit sets the systemvoltage that a power loss becomes a minimum, as the converter voltagecommand value, based on a power loss characteristics of the normalmodulation control which is a power loss characteristics of at least theinverter with respect to the system voltage in performing the normalmodulation control, and a power loss characteristics of theovermodulation control which is a power loss characteristics of at leastthe inverter with respect to the system voltage in performing theovermodulation control.

According to the controller for rotary electric machine apparatus of thepresent disclosure, the power loss characteristics of the normalmodulation control and the power loss characteristics of theovermodulation control, which are different in trend of characteristics,are calculated individually, and the converter voltage command valuethat the power loss becomes the minimum can be determined with goodaccuracy, based on two power loss characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of the rotary electric machineapparatus and the controller according to Embodiment 1;

FIG. 2 is a schematic block diagram of the controller according toEmbodiment 1;

FIG. 3 is a block diagram of the inverter control unit according toEmbodiment 1;

FIG. 4 is a figure for explaining the normal modulation controlaccording to Embodiment 1;

FIG. 5 is a figure for explaining the normal modulation control by theamplitude reduction modulation according to Embodiment 1;

FIG. 6 is a figure for explaining the overmodulation control accordingto Embodiment 1;

FIG. 7 is a block diagram of the converter voltage command calculationunit according to Embodiment 1;

FIG. 8 is a figure for explaining each control region according toEmbodiment 1;

FIG. 9 is a figure for explaining the power loss characteristics of theinverter and the rotary electric machine according to Embodiment 1;

FIG. 10 is a block diagram of the border voltage calculation unitaccording to Embodiment 1;

FIG. 11 is a figure for explaining the power loss characteristics of theinverter and the rotary electric machine according to Embodiment 1;

FIG. 12 is a figure for explaining the polynomial representing the powerloss characteristics of the first inverter and the first rotary electricmachine, and calculation of its coefficients according to Embodiment 1;

FIG. 13 is a figure for explaining the polynomial representing the powerloss characteristics of the second inverter and the second rotaryelectric machine, and calculation of its coefficients according toEmbodiment 1;

FIG. 14 is a figure for explaining the power loss characteristics of theconverter according to Embodiment 1;

FIG. 15 is a figure for explaining the polynomial representing the powerloss characteristic of the converter, and calculation of itscoefficients according to Embodiment 1;

FIG. 16 is a figure for explaining calculation of the candidate value ofthe converter voltage command value of the first combination accordingto Embodiment 1;

FIG. 17 is a figure for explaining calculation of the candidate value ofthe converter voltage command value of the second combination accordingto Embodiment 1;

FIG. 18 is a figure for explaining calculation of the candidate value ofthe converter voltage command value of the third combination accordingto Embodiment 1;

FIG. 19 is a figure for explaining calculation of the candidate value ofthe converter voltage command value of the fourth combination accordingto Embodiment 1; and

FIG. 20 is a hardware configuration diagram of the controller accordingto Embodiment 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS 1. Embodiment 1

A controller 400 for a rotary electric machine apparatus 1000(hereinafter, referred to simply as the controller 400) according toEmbodiment 1 will be explained with reference to the drawings. FIG. 1 isa schematic configuration diagram of the rotary electric machineapparatus 1000 and the controller 400 according to Embodiment 1 of thepresent disclosure.

The rotary electric machine apparatus 1000 is provided with a rotaryelectric machine MG, a converter 15, and an inverter IN. The rotaryelectric machine MG has plural-phase windings (in this example,three-phase). The converter 15 can raise a power source voltage Vb of adirect current power source B to output to system voltage lines 7, 8.The inverter IN is provided between the converter 15 and the rotaryelectric machine MG, and performs power conversion between the directcurrent power of the system voltage lines 7 and 8 and an alternatingcurrent power which drives the rotary electric machine MG.

1-1. Rotary Electric Machine

In the present embodiment, the rotary electric machine MG is used as adriving force source of wheels, and the rotary electric machineapparatus 1000 and the controller 400 are mounted on a vehicle (in thisexample, a hybrid vehicle).

In the present embodiment, a plurality of sets (in this example, 2 sets)of the rotary electric machine MG and the inverter IN are provided. Afirst rotary electric machine MG1 and a first inverter IN1 for the firstrotary electric machine MG1, and a second rotary electric machine MG2and a second inverter IN2 for the second rotary electric machine MG2 areprovided.

Each of the first and the second rotary electric machine MG1, MG2 isprovided with a stator fixed to a nonrotation member, and a rotor whichis disposed in radial-direction inner side of the stator and supportedrotatably. In the present embodiment, the rotary electric machine MG isa rotary electric machine of the permanent magnet synchronous type, thestator is provided with three-phase windings, and the rotor is providedwith permanent magnets. Each of the first and the second rotary electricmachine MG1, MG2 has a function of an electric motor and an electricgenerator.

In the present embodiment, the first rotary electric machine MG1operates as the electric generator driven by an internal combustionengine (not shown), and operates as the electric motor which starts theinternal combustion engine. The second rotary electric machine MG2 isconnected with the wheels via an output axis and reduction gears, whichare not shown, operates as the electric motor which drives the wheels,and operates as the electric generator which performs regenerative powergeneration by a driving force of the wheels.

Each of the first and the second rotary electric machine MG1, MG2 isprovided with a rotational angle sensor 28 (for example, a resolver) fordetecting a rotational angle θ of the rotor. An output signal of theeach rotational angle sensor 28 is inputted to the controller 400. Thecontroller 400 detects each rotational angle 61, 92 of the first and thesecond rotary electric machine MG1, MG2 based on the output signal ofthe each rotational angle sensor 28, and calculates each rotationalangle speed ω1, ω2 of the first and the second rotary electric machineMG1, MG2 based on the each rotational angle θ1, θ2.

1-2. Direct Current Power Source

A secondary battery, such as a nickel hydrogen or a lithium ion, is usedfor the direct current power source B. An electrical double layercapacitor and the like may be used for the direct current power sourceB. A positive electrode terminal of the direct current power source B isconnected to a power source side positive electric line 6 of theconverter 15, and a negative electrode terminal of the direct currentpower source B is connected to a power source side negative electricline 5 of the converter 15. A power source voltage sensor 10 fordetecting a power source voltage Vb of the direct current power source Bis provided. An output signal of the power source voltage sensor 10 isinputted to the controller 400.

1-3. Converter

A converter 15 is connected between the direct current power source Band the system voltage lines 7, 8, and is a DC-DC converter whichconverts direct current power. In the present embodiment, the converter15 is a voltage boosting and dropping converter having a function of avoltage boosting chopper which boosts a power source voltage Vb of thedirect current power source B and outputs to the system voltage lines 7,8, and a function of a voltage dropping chopper which drops a systemvoltage VH which is a DC voltage of the system voltage lines 7, 8 andoutputs to the direct current power source B. The converter 15 isprovided with a reactor, a switching device, and a free wheel diode atleast.

The converter 15 is provided with a smoothing capacitor C1 connectedbetween the power source side positive electric line 6 and the powersource side negative electric line 5. A relay (not shown), which isturned on at the time of vehicle operation and turned off at the time ofa vehicle operation stop, is provided between the positive electrodeterminal of the direct current power source B and the power source sidepositive electric lines 6, and between the negative electrode terminalof the direct current power source B and the power source side negativeelectric lines 5.

The converter 15 is provided with a reactor L1, two switching devicesQ1, Q2, two free wheel diodes D1, D2, and a smoothing capacitor C0. Eachof free-wheel diodes D1, D2 is connected in inverse parallel with eachof the switching devices Q1, Q2, respectively. The two switching devicesQ1, Q2 are connected in series between the positive electrode sidesystem voltage line 7 and the negative electrode side system voltageline 8. The reactor L1 is connected between a connection node connectingthe two switching devices Q1, Q2, and the power source side positiveelectric line 6. The smoothing capacitor C0 is connected between thepositive electrode side system voltage line 7 and the negative electrodeside system voltage line 8.

Between the positive electrode side system voltage line 7 and thenegative electrode side system voltage line 8, a system voltage sensor13 for detecting the system voltage VH of the system voltage lines 7, 8is provided. An output signal of the system voltage sensor 13 isinputted to the controller 400. Each of the two switching devices Q1, Q2is controlled on/off by each of converter control signals S1, S2outputted from the controller 400.

1-4. Inverter

The DC-voltage side of the first inverter IN1 and the second inverterIN2 are connected to the converter 15 via the common system voltagelines 7 and 8.

The first inverter IN1 is provided with three sets of a series circuit(leg) where a positive electrode side switching device Q11 (upper arm)connected to the positive electrode side system voltage line 7 and anegative electrode side switching device Q12 (lower arm) connected tothe negative electrode side system voltage line 8 were connected inseries, corresponding to each phase of the three-phase windings. That isto say, the first inverter IN1 is provided with a total of six switchingdevices of the three positive electrode side switching devices Q11U,Q11V, Q11W, and the three negative electrode side switching devicesQ12U, Q12V, Q12W. Each of free wheel diodes D11U, D11V, D11W, D12U,D12V, D12W is connected in inverse parallel with each of the switchingdevices Q11U, Q11V, Q11W, Q12U, Q12V, Q12W, respectively. Then, aconnection node between the positive electrode side switching device Q11and the negative electrode side switching device Q12 of each phase isconnected to the winding of the corresponding phase in the first rotaryelectric machine MG1. A current sensor 27 for detecting a current whichflows into the winding of each phase is provided on a wire of each phasewhich connects the connection node of a switching devices and thewinding. An output signal of the current sensor 27 is inputted to thecontroller 400. Each of the switching devices Q11U, Q11V, Q11W, Q12U,Q12V, Q12W is controlled on/off by each of first inverter controlsignals S11, S12, S13, S14, S15, S16 outputted from the controller 400,respectively.

In the similar manner, the second inverter IN2 is provided with threesets of a series circuit (leg) where a positive electrode side switchingdevice Q21 (upper arm) connected to the positive electrode side systemvoltage line 7 and a negative electrode side switching device Q22 (lowerarm) connected to the negative electrode side system voltage line 8 wereconnected in series, corresponding to each phase of the three-phasewindings. That is to say, the second inverter IN2 is provided with atotal of six switching devices of the three positive electrode sideswitching devices Q21U, Q21V, Q21W, and the three negative electrodeside switching devices Q22U, Q22V, Q22W. Each of the free wheel diodesD21U, D21V, D21W, D22U, D22V, D22W is connected in inverse parallel witheach of the switching devices Q21U, Q21V, Q21W, Q22U, Q22V, Q22W,respectively. Then, a connection node between the positive electrodeside switching device Q21 and the negative electrode side switchingdevice Q22 of each phase is connected to the winding of thecorresponding phase in the second rotary electric machine MG2. A currentsensor 27 for detecting a current which flows into the winding of eachphase is provided on a wire of each phase which connects the connectionnode of a switching devices and the winding. An output signal of thecurrent sensor 27 is inputted to the controller 400. Each of theswitching devices Q21U, Q21V, Q21W, Q22U, Q22V, Q22W is controlledon/off by each of second inverter control signals S21, S22, S23, S24,S25, S26 outputted from the controller 400, respectively.

By the switching control of the controller 400, the inverter IN1, IN2can convert DC voltage of the system voltage lines 7, 8 into three-phaseAC voltages, output to the rotary electric machine MG1, MG2, and canoperate the rotary electric machine MG1, MG2 as the electric motor,respectively. By the switching control of the controller 400, theinverter IN1, IN2 can convert three-phase AC voltages, which the rotaryelectric machine MG1, MG2 generated, into DC voltage, and output to thesystem voltage lines 7, 8, respectively.

As the switching devices of the converter 15 and the inverter IN1, IN2,IGBTs (Insulated Gate Bipolar Transistor), MOS (Metal OxideSemiconductor) transistors for power, bipolar transistors for power,SiC, GaN, or the like are used.

1-5. Controller

The controller 400 is provided with functional parts of a convertercontrol unit 750, a converter voltage command calculation unit 700, aninverter control unit 600, and the like, mentioned below. Each functionof the controller 400 is realized by processing circuits provided in thecontroller 400. In the present embodiment, as shown in FIG. 20, thecontroller 400 is provided with, as a processing circuit, an arithmeticprocessor (computer) 90 such as a CPU (Central Processing Unit), storageapparatuses 91 that exchange data with the arithmetic processor 90, aninput circuit 92 that inputs external signals to the arithmeticprocessor 90, an output circuit 93 that outputs signals from thearithmetic processor 90 to the outside, and the like.

As the arithmetic processor 90, ASIC (Application Specific IntegratedCircuit), IC (Integrated Circuit), DSP (Digital Signal Processor), FPGA(Field Programmable Gate Array), various kinds of logical circuits,various kinds of signal processing circuits, and the like may beprovided. As the arithmetic processor 90, a plurality of the same typeones or the different type ones may be provided, and each processing maybe shared and executed. As the storage apparatuses 91, there areprovided a RAM (Random Access Memory) which can read data and write datafrom the arithmetic processor 90, a ROM (Read Only Memory) which canread data from the arithmetic processor 90, and the like. The inputcircuit 92 is connected with various kinds of sensors and switches suchas the power source voltage sensor 10, the system voltage sensor 13, andthe current sensor 27, the rotational angle sensor 28, and is providedwith A/D converter and the like for inputting output signals from thesensors and the switches to the arithmetic processor 90. The outputcircuit 93 is connected with electric loads such as a gate drive circuitwhich drive on and off of the switching devices of the converter 15 andthe switching devices of the inverters IN1, IN2, and is provided withdriving circuit and the like for outputting a control signal from thearithmetic processor 90.

Then, the arithmetic processor 90 runs software items (programs) storedin the storage apparatus 91 such as a ROM and collaborates with otherhardware devices in the controller 400, such as the storage apparatus91, the input circuit 92, and the output circuit 93, so that the eachfunction of the control units 750, 700, 600 provided in the controller400 are realized. Setting data items such as map data be utilized in thecontrol units 750, 700, 600 are stored, as part of software items(programs), in the storage apparatus 91 such as a ROM. Each function ofthe controller 400 will be described in detail below.

1-5-1. Inverter Control Unit 600

The inverter control unit 600 calculates three-phase voltage commandvalues Vu, Vv, Vw, and controls the inverter IN based on the three-phasevoltage command values Vu, Vv, Vw to apply voltage to the three-phasewindings. The inverter control unit 600 controls on/off of the switchingdevices of the inverter IN so that the rotary electric machine MGoutputs torque of a torque command value Tqcom. Torque command valueTqcom is transmitted from an external controller of the controller 400,or other control units inside the controller 400. In the presentembodiment, the inverter control unit 600 performs current feedbackcontrol using a vector control method.

The inverter control unit 600 switches and performs a normal modulationcontrol in which the amplitudes of the three-phase voltage commandvalues Vu, Vv, Vw become less than or equal to a half value of thesystem voltage VH, and an overmodulation control in which the amplitudesof the three-phase voltage command values Vu, Vv, Vw exceed the halfvalue of the system voltage VH.

In the present embodiment, the inverter control unit 600 is providedwith a first inverter control unit 600 a which performs control of thefirst inverter IN1 and the first rotary electric machine MG1, and asecond inverter control unit 600 b which performs control of the secondinverter IN2 and the second rotary electric machine MG2.

Each of the first and the second torque command value Tqcom1, Tqcom2 isset to positive value or negative value according to driving condition.Especially at the time of regenerative braking of the hybrid vehicle,the second torque command value Tqcom2 is set to a negative value(Tqcom2<0). In this case, by the switching operation responded to thesecond inverter control signal S21 to S26, the second inverter IN2converts the AC voltage, which the second rotary electric machine MG2generated, into DC voltage, and supplies DC voltage (the system voltageVH) to the converter 15.

Since the first inverter control unit 600 a and the second invertercontrol unit 600 b are similar configurations, in the followingdescription, the first inverter control unit 600 a is explained as arepresentative.

As shown in FIG. 3, the first inverter control unit 600 a is providedwith a current command calculation unit 610, a current control unit 640,a three-phase voltage commands calculation unit 650, a PWM signalgeneration unit 660, a current coordinate conversion unit 620, and arotational angle speed detection unit 630.

1-5-1-1. Rotational Speed Detection Unit 630

The rotational speed detection unit 630 detects a rotational angle θ1 (amagnetic pole position) and a rotational angle speed ω1 of the rotor ofthe first rotary electric machine MG1, based on the output signal of therotational angle sensor 28 of the first rotary electric machine MG1.

1-5-1-2. Current Command Calculation Unit 610

<Calculation of dq-Axis Current Command Values>

The current command calculation unit 610 calculates a d-axis currentcommand value Idcom and a q-axis current command value Iqcom whichexpressed command values of the current which flows into the three-phasewindings of the first rotary electric machine MG1 with the dq-axisrotating coordinate system of the first rotary electric machine MG1. Thedq-axis rotating system consists of a d-axis defined in the direction ofthe N pole (magnetic pole position) of the permanent magnet provided inthe rotor of the first rotary electric machine MG1 and a q-axis definedin the direction advanced to d-axis by 90 degrees (π/2) in an electricalangle, and which is the two-axis rotating coordinate system whichrotates synchronizing with rotation of the rotor in the electricalangle.

<Maximum Torque/Current Control, Field Weakening Control>

The current command calculation unit 610 calculates the d-axis currentcommand value Idcom and the q-axis current command value Iqcom whichmakes the first rotary electric machine MG1 output a torque of the firsttorque command value Tqcom1. The current command calculation unit 610calculates the dq-axis current command values Idcom, Iqcom in accordancewith the current vector control method of a maximum torque/currentcontrol, a field weakening control and the like. In the maximumtorque/current control, the dq-axis current command values Idcom, Iqcomwhich maximize the generated torque for the same current are calculated.In the field weakening control, the d-axis current command value Idcomis made to increase in the negative direction rather than the dq-axiscurrent command values Idcom, Iqcom calculated in the maximumtorque/current control, and the magnetic flux of the permanent magnet isweakened. In the field weakening control, the dq-axis current commandvalues Idcom, Iqcom are moved on a constant induced voltage ellipse (avoltage-limiting ellipse) according to the first torque command valueTqcom1.

The current command calculation unit 610 calculates the dq-axis currentcommand values Idcom, Iqcom corresponding to the first torque commandvalue Tqcom1, by use of a map data in which the relationship between thefirst torque command value Tqcom1 and the dq-axis current command valuesIdcom, Iqcom is preliminarily set for each control method.

The current command calculation unit 610 calculates the dq-axis currentcommand values by the maximum torque/current control under the operatingcondition which can perform the maximum torque/current control; andcalculates the dq-axis current command values by the field weakeningcontrol under the operating condition which cannot perform thecalculation of the dq-axis current command values by the maximumtorque/current control owing to limitation of the voltage-limitingellipse.

1-5-1-3. Current Coordinate Conversion Unit 620

The current coordinate conversion unit 620 converts three-phase currentsIu, Iv, Iw, which flow into the winding of each phase detected based onthe output signal of the current sensor 27 of the first rotary electricmachine MG1, into a d-axis current Id and a q-axis current Iqrepresented in the dq axial rotation coordinate system by performing athree-phase/two-phase conversion and a rotating coordinate conversionbased on the magnetic pole position θ1.

1-5-1-4. Current Control Unit 640

The current control unit 640 performs a current feedback control whichchanges, by PI control and the like, a d-axis voltage command value Vd #and a q-axis voltage command value Vg # which represent a command signalof the voltage applied to the first rotary electric machine MG1 in thedq-axis rotating coordinate system, so that the dq-axis currents Id, Iqapproach the dq-axis current command values Idcom, Iqcom.

1-5-1-5. Three-Phase Voltage Commands Calculation Unit 650

<Coordinate Conversion>

Then, the three-phase voltage commands calculation unit 650 converts thedq-axis voltage command values Vd #, Vq # into three-phase AC voltagecommand values Vuc, Vvc, Vwc after coordinate conversion, by performinga fixed coordinate conversion and a two-phase/three-phase conversionbased on the magnetic pole position θ1. These three-phase voltagecommand values Vuc, Vvc, Vwc after coordinate conversion become sinewaves, and correspond to the fundamental wave components of thethree-phase voltage command values or the applied voltages of thethree-phase windings.

<Amplitude Reduction Modulation>

The three-phase voltage commands calculation unit 650 calculates finalthree-phase voltage command values Vu, Vv, Vw by applying an amplitudereduction modulation to the three-phase voltage command values Vuc, Vvc,Vwc after the coordinate conversion of sine waves. At least when amodulation rate M of the three-phase voltage command values aftercoordinate conversion becomes larger than 1, the three-phase voltagecommands calculation unit 650 applies the amplitude reductionmodulation, which reduces amplitudes of the three-phase voltage commandvalues while maintaining line voltages of the three-phase voltagecommand values, to the three-phase voltage command values aftercoordinate conversion.

The modulation rate M of the three-phase voltage command values is aratio of an amplitude VA of the fundamental wave component of thethree-phase voltage command values or the applied voltages of thethree-phase windings, with respect to the half value of the systemvoltage VH, as shown in a next equation. The fundamental wave componentsof the three-phase voltage command values become the same as thethree-phase voltage command values after coordinate conversion.M=VA×2/VH  (1)<Normal Modulation Control or Overmodulation Control>

As explained below, since the amplitude reduction modulation isperformed in the present embodiment, when the modulation rate M is lessthan or equal to 1.15, it becomes the state where the normal modulationcontrol is performed, and when the modulation rate M is larger than1.15, it becomes the state where the overmodulation control isperformed.

1) When M<=1.15

The state where the normal modulation control is performed

2) When M>1.15

The state where the overmodulation control is performed

<The State where the Normal Modulation Control is Performed (M<=1)>

When the modulation rate M is less than or equal to 1, even if themodulation is not applied, the voltage saturation in which theamplitudes of the three-phase voltage command values after coordinateconversion exceed the half value of the system voltage VH does notoccur, but it becomes the state where the normal modulation control isperformed.

As shown in FIG. 4, in the state where the normal modulation control ofM<=1 is performed, the voltage command value of the sine wave does notexceed the vibration range of the carrier wave (−VH/2 to VH/2) describedbelow, but the switching signal is turned on and off with the duty ratioaccording to the voltage command value.

<The State where the Normal Modulation Control Due to the AmplitudeReduction Modulation is Performed (1<M<=1.15)>

In the case where the amplitude reduction modulation is not applied,when the modulation rate M becomes larger than 1, the voltage saturationin which the amplitudes of the three-phase voltage command values aftercoordinate conversion exceed the half value of the system voltage VHoccurs, and it becomes the state where the overmodulation control isperformed.

On the other hand, by applying the amplitude reduction modulation, untilthe modulation rate M becomes larger than 2/√3 (≈1.15), the voltagesaturation in which the amplitudes of the three-phase voltage commandvalues after amplitude reduction modulation exceed the half value of thesystem voltage VH does not occur, and it becomes the state where thenormal modulation control is performed. Various well-known methods, suchas third-order harmonic wave superimposing, the min-max method (pseudothird-order harmonic wave superimposing), two-phase modulation, andtrapezoidal wave modulation, are used for the method of the amplitudereduction modulation. The third-order harmonic wave superimposing is themethod that superimposes a third-order harmonic wave on the three-phasevoltage command values after coordinate conversion. The min-max methodis the method that superimposes ½ of a middle voltage of the three-phasevoltage command values after coordinate conversion on the three-phasevoltage command values after coordinate conversion. The two-phasemodulation is the method that fixes any one phase of the voltage commandvalues to 0 or the system voltage VH, and modulates other two phases sothat line voltage of the three-phase voltage command values aftercoordinate conversion do not change.

As shown in FIG. 5, in the state of <M<=1.1.5 where the normalmodulation control by the amplitude reduction modulation is performed,by the amplitude reduction modulation (in this example, the min-maxmethod), the voltage command values are reduced so as not to exceed thevibration range of the carrier wave (−VH/2 to VH/2), and the switchingsignal is turned on and off with the duty ratio according to the voltagecommand value.

<The State where the Overmodulation Control is Performed (1.15<M<=1.27)>

On the other hand, when the modulation rate M becomes larger than 2/√3(≈1.15), even if the amplitude reduction modulation is performed, thevoltage saturation in which the amplitudes of three-phase voltagecommand values exceed the half value of the system voltage VH occurs,and it becomes the state where the overmodulation control is performed.The modulation rate M can be increased up to the maximum value 4/π(≈1.27) at which the voltage command value becomes a rectangular wave.When the modulation rate M is increased to 1.27, the three-phase voltagecommand values become rectangular waves, harmonic wave components becomelarge and torque ripple components increase. Therefore, in the presentembodiment, in order to suppress increase in the torque ripplecomponents, the maximum set value of the modulation rate M is set to avalue lower than 1.27, for example, 1.21.

As shown in FIG. 6, in the state of 1.15<M<=1.27 where theovermodulation control is performed, in interval when the voltagecommand value exceeds over the vibration range of the carrier wave(−VH/2 to VH/2) and the voltage saturation occurs, the switching signalis not turned on and off with the duty ratio according to the voltagecommand value, but it remains turned on or turned off. Therefore, in theovermodulation control, the number of turning the switching device onand off becomes less than the normal modulation control, and switchingloss is reduced.

1-5-1-6. PWM Signal Generation Unit 660

The PWM signal generation unit 660 turns on and off the plurality ofswitching devices by PWM (Pulse Width Modulation) control based on thethree-phase voltage command values Vu, Vv, Vw. The PWM signal generationunit 660 generates switching signals which turn on and off the switchingdevices of each phase, by comparing each of the three-phase voltagecommand values and the carrier wave. The carrier wave is a triangularwave which vibrates with an amplitude of ½ of the system voltage VHcentering on 0 with a carrier frequency. The PWM signal generation unit660 turns on the switching signal when the voltage command value exceedsthe carrier wave, and turns off the switching signal when the voltagecommand value is below the carrier wave. The switching signal istransmitted as it is to the positive electrode side switching device,and a switching signal which reversed the switching signal istransmitted to the negative electrode side switching device. Eachswitching signal S11 to S16 is inputted into the gate terminal of eachswitching device of the first inverter IN1 via the gate drive circuit,and each switching device is turned on or turned off.

1-5-2. Converter Control Unit 750

The converter control unit 750 controls the converter 15 so that thesystem voltage VH which is the DC voltage of the system voltage lines 7,8 approaches a converter voltage command value VH #, when the convertervoltage command value VH # is larger than the power source voltage Vb.In the present embodiment, the converter control unit 750 detects thepower source voltage Vb based on an output signal of the power sourcevoltage sensor 10, and detects the system voltage VH based on an outputsignal of the system voltage sensor 13. The converter control unit 750changes the duty ratio of the converter control signals S1 to S2according to a PWM control method based on the system voltage VH and theconverter voltage command value VH #.

When performing a voltage boosting operation to the converter 15, forexample the converter control unit 750 sets alternately the ON periodwhich turns on only the positive electrode side switching device Q1 andthe ON period which turns on only the negative electrode side switchingdevice Q2, and changes the ratio of the two ON periods to change avoltage boosting ratio. When performing a voltage dropping operation tothe converter 15, for example the converter control unit 750 setsalternately the ON period which turns on only the positive electrodeside switching device Q1 and the OFF period which turns off all theswitching devices Q1, Q2, and changes the ratio of the ON period and theOFF period to change a voltage dropping ratio. When the convertervoltage command value VH # is smaller than or equal to the power sourcevoltage Vb, the converter control unit 750 turns off all the switchingdevices Q1, Q2, and changes the direct current power source B and thesystem voltage lines 7, 8 into the direct connection state.

At the time of the voltage boosting operation, the converter 15 suppliesthe system voltage VH, which boosted the power source voltage Vbsupplied from the direct current power source B, to the inverter IN1,IN2 in common. At the time of the voltage dropping operation, theconverter 15 drops the system voltage VH supplied from the inverter IN1,IN2 via the smoothing capacitor C0, and supplies it to the directcurrent power source B.

1-5-3. Converter Voltage Command Calculation Unit 700

The converter voltage command calculation unit 700 calculates theconverter voltage command value VH # within a range which is larger thanor equal to the power source voltage Vb and is smaller than or equal tothe output upper limit voltage Vcnmax of the converter. In the presentembodiment, as shown in FIG. 7, the converter voltage commandcalculation unit 700 is provided with a border voltage calculation unit800, a motor output calculation unit 801, a loss characteristiccalculation unit 802, and a voltage command calculation unit 803.

1-5-3-1. Border Voltage Calculation Unit 800

Since a counter electromotive force of the rotary electric machine MGincreases and an induced voltage becomes high when the rotational anglespeed w and torque increase, a border voltage Vmg which is the minimumsystem voltage VH required in the case of performing the normalmodulation control becomes high. In order to perform the normalmodulation control, it is necessary to make the system voltage VH higherthan the border voltage Vmg. On the other hand, there is a limit in thevoltage boosting of the converter 15, and there is an upper limit value(the output upper limit voltage Vcnmax) in the output voltage (systemvoltage VH) of the converter 15.

The border voltage calculation unit 800 calculates the border voltageVmg which is the minimum system voltage VH required in the case ofperforming the normal modulation control under conditions of the presenttorque command value Tqcom and the present rotational angle speed ω ofthe rotary electric machine MG.

In the present embodiment, the maximum torque current control isperformed in performing the normal modulation control. FIG. 8 shows atorque-rotational angle speed characteristics for explaining anexecutable region of the maximum torque/current control. A vertical axisis the torque of the rotary electric machine MG, a horizontal axis isthe rotational angle speed ω of the rotary electric machine MG, and thesolid line in the figure shows a maximum torque line at each rotationalangle speed a in the case of performing the maximum torque/currentcontrol. In the case where the rotational angle speed ω is smaller thanor equal to a base rotational angle speed, the maximum output torque ofthe rotary electric machine MG is determined by restricting the currentof the rotary electric machine MG to a rated current, and becomes aconstant value to a change of the rotational angle speed ω. In the casewhere the rotational angle speed ω is larger than the base rotationalangle speed, the maximum output torque of the rotary electric machine MGis determined by restricting a line voltage of the rotary electricmachine MG to the system voltage VH, and decreases as the rotationalangle speed ω increases.

A plurality of solid line curves of FIG. 8 show a change of the maximumtorque line of the maximum torque/current control when changing thesystem voltage VH. As shown in FIG. 8, as the system voltage VH isboosted from the power source voltage Vb to the output upper limitvoltage Vcnmax, the maximum torque line and the base rotational speedcan be shifted to the high rotational angle speed side, and theexecutable region of the maximum torque/current control can be expanded.In the case where the system voltage VH is the output upper limitvoltage Vcnmax, the base rotational angle speed becomes the highest andthe executable region of the maximum torque/current control becomes thewidest.

A region of high rotation angular speed side and high torque side ratherthan the executable region of the maximum torque/current controlcorresponding to this output upper limit voltage Vcnmax is an executableregion of the field weakening control when the system voltage VH is theoutput upper limit voltage Vcnmax.

In the present embodiment, the maximum torque/current control isperformed even in a part of the execution region of the overmodulationcontrol where the modulation rate M is larger than 1.15 (for example,1.15<M<=1.21). As shown in FIG. 8 by hatching, the execution region ofthe normal modulation control is a region where the modulation rate Mbecomes less than or equal to 1.15 in the executable region of themaximum torque/current control. Therefore, in the case where themodulation rate M is increased to the modulation rate M of the boundarybetween the normal modulation control and the overmodulation control (inthis example, M=1.15), the border voltage Vmg is the minimum systemvoltage VH required in the case of performing the maximum torque/currentcontrol. A region where the system voltage VH is less than or equal tothe border voltage Vmg is the executable region of the normal modulationcontrol, and a region where the system voltage VH is larger than theborder voltage Vmg is the executable region of overmodulation control.

FIG. 9 is a figure which plotted equal torque curves of each torque at acertain rotational angle speed, in the case where a vertical axis is apower loss of the inverter IN and the rotary electric machine MG, and ahorizontal axis is the system voltage VH. Since a large motor current isgenerally necessary in order to generate a large torque, a loss becomeslarge accordingly. A dotted line in FIG. 9 shows the line of the bordervoltage Vmg where the execution region of the normal modulation controland the execution region of the overmodulation control switch. As seenfrom FIG. 9, in each equal torque curve, the power loss of the inverterIN and the rotary electric machine MG becomes the minimum in the lineshown by the dashed dotted line which is little lower than the line ofthe border voltage Vmg.

As the system voltage VH is reduced rather than the line of the minimumpower loss, the power loss of the inverter IN and the rotary electricmachine MG increases gradually. In order to maintain the output torqueagainst the drop of the system voltage VH, it is necessary to lower theinduced voltage. For that purpose, the d-axis current is increased tothe negative direction, and the magnetic flux of the permanent magnet isweakened. As a result, as the system voltage VH is lowered, the windingcurrent increases, and the energization loss of the inverter IN and thecopper loss of the rotary electric machine MG increase.

<Detailed Configuration of the Border Voltage Calculation Unit 800>

The detailed configuration of the border voltage calculation unit 800will be explained. The border voltage calculation unit 800, about thefirst rotary electric machine MG, calculates the first border voltageVmg1 which is the minimum system voltage VH required in the case ofperforming the normal modulation control of the first rotary electricmachine MG1 under the conditions of the present torque command valueTqcom1 and the present rotational angle speed ω1 of the first rotaryelectric machine MG1. The border voltage calculation unit 800, about thesecond rotary electric machine MG2, calculates the second border voltageVmg2 which is the minimum system voltage VH required in the case ofperforming the normal modulation control of the second rotary electricmachine MG2 under the conditions of the present torque command valueTqcom2 and the present rotational angle speed ω2 of the second rotaryelectric machine MG2.

In the present embodiment, as shown in FIG. 10, the border voltagecalculation unit 800 is provided with a first normal modulation currentcommand calculation unit 1110 a, a second normal modulation currentcommand calculation unit 1110 b, a first inductance calculation unit1120 a, a second inductance calculation unit 1120 b, a first bordervoltage calculation unit 1130 a, and a second border voltage calculationunit 1130 b.

The first normal modulation current command calculation unit 1110 acalculates first normal modulation dq-axis current command valuesIdcom_loss1, Iqcom_loss1 which make the first rotary electric machineMG1 output the first torque command value Tqcom1 by performing thenormal modulation control and the maximum torque/current control. Thefirst normal modulation current command calculation unit 1110 acalculates the dq-axis current command values by the similar method asthe current command calculation unit 610 of the first inverter controlunit 600 a.

In the present embodiment, the first normal modulation current commandcalculation unit 1110 a calculates the first normal modulation dq-axiscurrent command values Idcom_loss1, Iqcon_loss1 on a fixed operatingcondition of a preliminarily set rotational angle speed (for example,ω1=0) smaller than or equal to the base rotational speed. According tothis configuration, even if the present operating condition is theexecution region of the overmodulation control, the current commandvalues for the normal modulation control can be calculated certainly.

The first normal modulation current command calculation unit 1110 acalculates the first normal modulation dq-axis current command valuesIdcom_loss1, Iqcom_loss1 corresponding to the first torque command valueTqcom1, by using a map data in which the relationship between the firsttorque command value Tqcom1 and the first normal modulation dq-axiscurrent command values Idcom_loss1, Iqcom_loss1 is preliminarily set.The map data is preliminarily set based on measured value or magneticfield analysis. The q-axis current command value and d-axis currentcommand value corresponding to the each torque command value are set tothe map data at the interval (unit) of predetermined torque commandvalue.

The first inductance calculation unit 1120 a calculates first dq-axisinductances Ld_loss1, Lq_loss1 of the first rotary electric machine MG1corresponding to the first normal modulation dq-axis current commandvalues Idcom_loss1, Iqcom_loss1. The first inductance calculation unit1120 a calculates the first dq-axis inductances Ld_loss1, Lq_loss1corresponding to the first normal modulation dq-axis current commandvalues Idcom_loss1, Iqcom_loss1, by using a map data in which therelationship between the first normal modulation dq-axis current commandvalues Idcom_loss1, Iqcom_loss1 and the first dq-axis inductancesLd_loss1, Lq_loss1 is preliminarily set.

The first border voltage calculation unit 1130 a calculates the firstborder voltage Vmg1 using a next equation, based on the first normalmodulation dq-axis current command values Idcont_loss1, Iqcont_loss1,the first dq-axis inductances Ld_loss1, Lq_loss1, and the rotationalangle speed al of the first rotary electric machine MG1.

$\begin{matrix}{{{Vmg}\; 1} = {\frac{M\mspace{14mu}\max}{\eta 1}\sqrt{( {{R\;{1 \cdot {Idcom\_ loss1}}} - {{\omega 1} \cdot {Lq\_ loss1} \cdot {Iqcom\_ loss1}}} )^{2} + \begin{matrix}( {{R\;{1 \cdot {Idcom\_ loss1}}} + {{\omega 1} \cdot {Ld\_ loss1} \cdot}}  \\ {{Idcom\_ loss1} + {{\omega 1} \cdot {\varphi{mag}1}}} )^{2}\end{matrix}}}} & (2)\end{matrix}$

Herein, Mmax is the maximum value of the modulation rate M of theexecution region of the normal modulation control (in this example,1.15). η1 expresses a ratio which converts the system voltage VH intothe line voltage of the first rotary electric machine MG1. Therefore,the equation (2) calculates, by calculation of the square root, theminimum line voltage of the first rotary electric machine MG1 requiredin the case of performing the normal modulation control and the maximumtorque/current control of the first rotary electric machine MG1, andconverts the line voltage into the system voltage using η1. R1 is theresistance of the winding of the stator of the first rotary electricmachine MG1, and ψmag1 is the magnetic flux of the permanent magnet ofthe rotor of the first rotary electric machine MG1.

By the similar method as the first normal modulation current commandcalculation unit 1110 a, the second normal modulation current commandcalculation unit 1110 b calculates second normal modulation dq-axiscurrent command values Idcom_loss2, Iqcom_loss2 which make the secondrotary electric machine MG2 output the second torque command valueTqcom2 by performing the normal modulation control and the maximumtorque/current control.

By the similar method as the first inductances calculation unit 1120 a,the second inductances calculation unit 1120 b calculates second dq-axisinductances Ld_loss2, Lq_loss2 of the second rotary electric machinesMG2 corresponding to the second normal modulation dq-axis currentcommand values Idcom_loss2, Iqcom_loss2.

The second border voltage calculation unit 1130 b calculates the secondborder voltage Vmg2 using a next equation, based on the second normalmodulation dq-axis current command values Idcom_loss2, Iqcom_loss2, thesecond dq-axis inductances Ld_loss2, Lq_loss2, and the rotational anglespeed ω2 of the second rotary electric machine MG2.

$\begin{matrix}{{{Vmg}\; 2} = {\frac{M\mspace{14mu}\max}{\eta 2}\sqrt{( {{R\;{2 \cdot {Idcom\_ loss2}}} - {{\omega 2} \cdot {Lq\_ loss2} \cdot {Iqcom\_ loss2}}} )^{2} + \begin{matrix}( {{R\;{2 \cdot {Idcom\_ loss2}}} + {{\omega 2} \cdot {Ld\_ loss2} \cdot}}  \\ {{Idcom\_ loss2} + {{\omega 2} \cdot {\varphi{mag}2}}} )^{2}\end{matrix}}}} & (3)\end{matrix}$

η2 expresses a ratio which converts the system voltage VH into the linevoltage of the second rotary electric machines MG2. R2 is the resistanceof the winding of the stator of the second rotary electric machine MG2,and ψmag2 is the magnetic flux of the permanent magnet of the rotor ofthe second rotary electric machine MG2.

1-5-3-2. Motor Output Calculation Unit 801

As shown in FIG. 7, the converter voltage command calculation unit 700is provided with the motor output calculation unit 801. The motor outputcalculation unit 801 calculates an output PMOT of the rotary electricmachine MG by multiplying the torque command value Tqcom and therotational angle speed ω. In the present embodiment, the motor outputcalculation unit 801 calculates an output PMOT_mg1 of the first rotaryelectric machine MG1 by multiplying the first torque command valueTqcom1 and the first rotational angle speed ω1. The motor outputcalculation unit 801 calculates an output PMOT_mg2 of the second rotaryelectric machine MG2 by multiplying the second torque command valueTqcom2 and the second rotational angle speed ω2. Then, the motor outputcalculation unit 801 calculates a sum total output PMOT_ALL of tworotary electric machines by totaling the output PMOT_mg1 of the firstrotary electric machine MG1 and the output PMOT_mg2 of the second rotaryelectric machine MG2.

1-5-3-3. Loss Characteristic Calculation Unit 802

<Calculation of Power Loss Characteristics of Normal Modulation Control,and Power Loss Characteristics of Overmodulation Control>

Similarly to FIG. 9, FIG. 11 is a figure which plotted an equal torquecurve of a certain torque at a certain rotational angle speed, in thecase where a vertical axis is a power loss of the inverter IN and therotary electric machine MG and a horizontal axis is the system voltageVH. The trends of the power loss characteristics are different among theexecution region of the normal modulation control and the maximumtorque/current control, the execution region of the overmodulationcontrol and the maximum torque/current control, and the execution regionof the overmodulation control and the field weakening control.

In the execution region of the normal modulation control and the maximumtorque/current control, as the system voltage VH decreases, the powerloss decreases gradually at small gradient. In the execution region ofthe overmodulation control and the maximum torque/current control, asthe system voltage VH decreases, the modulation rate M increases, theswitching frequency of the switching device decreases, and the switchingloss decreases. Therefore, the power loss decreases gradually at largergradient than the execution region of the normal modulation control andthe maximum torque/current control. In the execution region of theovermodulation control and the field weakening control, as the systemvoltage VH decreases, after the power loss decreases gradually for awhile, the power loss increases gradually by increase in the copper lossand the energization loss.

Characteristics of the power loss are largely different between theexecution region of the overmodulation control and the execution regionof the normal modulation control. That is to say, combining theexecution region of the overmodulation control and the maximumtorque/current control, and the execution region of the overmodulationcontrol and the field weakening control, the power lose can beapproximated by a quadratic function of downwardly projected. In theexecution region of normal modulation control, the power loss can beapproximated by a linear function.

Then, the loss characteristic calculation unit 802 calculates a powerloss characteristics of the normal modulation control which is a powerloss characteristics of the rotary electric machine and the inverterwith respect to the system voltage VH in performing the normalmodulation control, and a power loss characteristics of theovermodulation control which is a power loss characteristics of therotary electric machine and the inverter with respect to the systemvoltage VH in performing the overmodulation control. In the presentembodiment, the loss characteristic calculation unit 802 calculates thepower loss characteristics of the normal modulation control, and thepower loss characteristics of the overmodulation control, about each ofthe first rotary electric machine MG1 and the second rotary electricmachine MG2.

In the present embodiment, the loss characteristic calculation unit 802calculates coefficients of the polynomial (in this example, 2nd-orderpolynomial) in which the system voltage VH is a variable, as the powerloss characteristics of the normal modulation control and the power losscharacteristics of the overmodulation control.

The polynomial representing each power loss characteristics is a2nd-order polynomial showing in each of next equations. Herein,Ploss_mg1_1 is the power loss of the normal modulation control of thefirst rotary electric machine MG1, Ploss_mg1_2 is the power loss of theovermodulation control of the first rotary electric machine MG1,Ploss_mg2_1 is the power loss of the normal modulation control of thesecond rotary electric machine MG2, and Ploss_mg2_2 is the power loss ofthe overmodulation control of the second rotary electric machine MG2.Ploss_mg1_1(VH)=α_mg1_1·VH ²+β_mg1_1·VH+γ_mg1_1  (4)Ploss_mg1_2(VH)=α_mg1_2·VH ²+β_mg1_2·VH+γ_mg1_2  (5)Ploss_mg2_1(VH)=α_mg2_1·VH ²+β_mg2_1·VH+γ_mg2_1  (6)Ploss_mg2_2(VH)=α_mg2_2·VH ²+β_mg2_2·VH+γ_mg2_2  (7)

The loss characteristic calculation unit 802 calculates each ordercoefficient α, β, and γ of the polynomial of each power losscharacteristics of the equation (4) to the equation (7). In the presentembodiment, as shown in FIG. 12, about each order coefficient of eachthe power loss characteristics of the first rotary electric machine MG1,by use of a relation characteristic in which a relationship among theoutput torque of the first rotary electric machine MG1, the rotationalangle speed ω1 of the first rotary electric machine MG1, and eachcoefficient is preliminarily set, the loss characteristic calculationunit 802 calculates each coefficient corresponding to the present torquecommand value Tqcom1 and the present rotational angle speed ω1 of thefirst rotary electric machine MG1. As shown in FIG. 13, about each ordercoefficient of each the power loss characteristics of the second rotaryelectric machine MG2, by use of a relation characteristic in which arelationship among the output torque of the second rotary electricmachine MG2, the rotational angle speed ω2 of the second rotary electricmachine MG2, and each coefficient is preliminarily set, the losscharacteristic calculation unit 802 calculates each coefficientcorresponding to the present torque command value Tqcom2 and therotational angle speed ω2 of the second rotary electric machine MG2. Mapdata and the like is used for the relation characteristic. The relationcharacteristic of each coefficient is preliminarily set using the leastsquare method, based on measured loss data, or loss data calculated bymagnetic field analysis and loss calculation of the inverter at everytorque of rotary electric machine and rotational angle speed of rotaryelectric machine, for example.

<Calculation of Power Loss Characteristics of Converter>

First, the power loss characteristics of the converter 15 will beexplained. FIG. 14 shows the power loss characteristics of the converter15. A horizontal axis is the system voltage VH and a vertical axis isthe power loss of the converter 15. They are characteristics when thepower source voltage Vb is fixed and the output of the converter ischanged. Equal output curves at each output of the converter areplotted. At each output of the converter, as the system voltage VHincreases, the power loss of the converter increases. At each systemvoltage VH, as the output of the converter increases, the power loss ofthe converter increases.

The loss characteristic calculation unit 802 calculates the power losscharacteristics of the converter with respect to the system voltage VH.In the present embodiment, the loss characteristic calculation unit 802calculates coefficients of the polynomial (in this example, a polynomialwhose order is smaller than or equal to the 2nd-order) in which thesystem voltage VH is a variable, as the power loss characteristics ofthe converter.

The polynomial representing the power loss characteristics of theconverter is a 2nd-order polynomial showing in a next equation.Ploss_dcdc is the power loss of the converter.Ploss_dcdc(VH)=α_dcdc·VH ²+β_dcdc·VH+γ_dcdc  (8)

The loss characteristic calculation unit 802 calculates each ordercoefficient α, β, and γ of the polynomial of the power losscharacteristics of the converter of the equation (8). In the presentembodiment, as shown in FIG. 15, about each order coefficient of thepower loss characteristics of the converter, by use of a relationcharacteristic in which a relationship between the power source voltageVb and the output (output power) of the converter 15 is preliminarilyset, the loss characteristic calculation unit 802 calculates eachcoefficient corresponding to the present power source voltage Vb and thepresent output of the converter 15. Map data and the like is used forthe relation characteristic. The relation characteristic of eachcoefficient is preliminarily set using the least square method, based onmeasured loss data of the converter 15, or loss data calculated by losscalculation of the converter 15 at every the converter output and thepower source voltage Vb, for example.

As mentioned above, each power loss characteristics are approximated bythe 2nd-order polynomial in which the system voltage VH is the variable,and each order coefficient is calculated using the relationcharacteristic between two variables. Therefore, compared with the casewhere each power loss characteristics is not approximated by thepolynomial, but is approximated by a relation characteristic of threevariables which are the system voltage VH and two variables, combinationcan be reduced significantly and the storage capacity can be reducedsignificantly. The computation load in the voltage command calculationunit 803 described below can also be reduced significantly.

1-5-3-4. Voltage Command Calculation Unit 803

The voltage command calculation unit 803 sets the system voltage VH thata power loss becomes the minimum, as the converter voltage command valueVH #, based on the power loss characteristics of the normal modulationcontrol and the power loss characteristics of the overmodulationcontrol.

According to this configuration, the power loss characteristics of thenormal modulation control and the power loss characteristics of theovermodulation control, which are different in trend of characteristics,are calculated individually, and the converter voltage command value VH# that the power loss becomes the minimum can be determined with goodaccuracy based on two power loss characteristics.

In the present embodiment, the voltage command calculation unit 803calculates a minimum value of the power loss in performing the normalmodulation control, and the system voltage VH at the calculated minimumvalue of the power loss, based on the power loss characteristics of thenormal modulation control; and calculates a minimum value of the powerloss in performing the overmodulation control, and the system voltage VHat the calculated minimum value of the power loss, based on the powerloss characteristics of the overmodulation control. Then, the voltagecommand calculation unit 803 determines any smaller one of the minimumvalue of the power loss in performing the normal modulation control, andthe minimum value of the power loss in performing the overmodulationcontrol, and sets the system voltage at the determined smaller one, asthe converter voltage command value VH #.

According to this configuration, based on each power losscharacteristics, the minimum value of the power loss in performing thenormal modulation control and the minimum value of the power loss inperforming the overmodulation control can be calculated with goodaccuracy, and the system voltage VH corresponding to the minimum valueof the power loss of modulation control with smaller power loss can beset as the converter voltage command value VH #.

In the present embodiment, since a plurality of sets of the rotaryelectric machine MG and the inverter IN are provided, the voltagecommand calculation unit 803 sets the system voltage VH that a powerloss obtained by totaling a plurality of sets becomes a minimum, as theconverter voltage command value VH #, based on each set of the powerloss characteristics of the normal modulation control and the power losscharacteristics of the overmodulation control. The voltage commandcalculation unit 803 sets the system voltage VH that a sum total powerloss of the rotary electric machine, the inverter, and the converterbecomes a minimum, as the converter voltage command value VH #, based onthe power loss characteristics of the normal modulation control, thepower loss characteristics of the overmodulation control, and the powerloss characteristics of the converter.

According to this configuration, even if a plurality of sets of therotary electric machine MG and the inverter IN are provided, based oneach set of the power loss characteristics of the normal modulationcontrol and the power loss characteristics of the overmodulationcontrol, the system voltage VH that the power loss obtained by totalinga plurality of sets becomes the minimum can be set as the convertervoltage command value VH #.

About each of a plurality of combinations which combined the case wherethe normal modulation control or the overmodulation control is performedin each set, the voltage command calculation unit 803 calculates aminimum value of sum total power loss based on each set of the powerloss characteristics of the normal modulation control or the power losscharacteristics of the overmodulation control, and calculates the systemvoltage at the calculated minimum value as a candidate value VHtp of theconverter voltage command value. Then, the voltage command calculationunit determines a combination that the minimum value of the power lossbecomes the smallest in the plurality of combinations, and sets thecandidate value VHtp of the converter voltage command value in thedetermined combination as the converter voltage command value VH #.

According to this configuration, about each combination, the minimumvalue of the sum total power loss of each combination can be calculatedwith good accuracy based on each set of the power loss characteristicsof the normal modulation control or the power loss characteristics ofovermodulation control corresponding to each combination. Then, thecombination that sum total power loss becomes the minimum in theplurality of combinations is determined, and the candidate value VHtp ofthe converter voltage command value of the determined combination can beset as the converter voltage command value VH #.

About each of the plurality of combinations, the voltage commandcalculation unit 803 totals the coefficients of corresponding respectivepower loss characteristics for each order of the polynomials, andcalculates the minimum value of sum total power loss, and the candidatevalue VHtp of the converter voltage command value corresponding to theminimum value of sum total power loss, based on the total value of eachorder coefficient.

According to this configuration, by calculating the total value of eachorder coefficient about the plurality of power loss characteristics ofeach combination, each value can be calculated using total power losscharacteristics. Therefore, computation load can be significantlyreduced rather than the case of calculating using each power losscharacteristics individually.

In the present embodiment, since 2 sets of the rotary electric machineMG and the inverter IN are provided, the number of combination becomes4. As follows, the first combination is set to the case where the normalmodulation control is performed in both of the first rotary electricmachine MG1 and the second rotary electric machine MG2. The secondcombination is set to the case where the overmodulation control isperformed in both of the first rotary electric machine MG1 and thesecond rotary electric machine MG2. The third combination is set to thecase where the normal modulation control is performed in the firstrotary electric machine MG1 and the overmodulation control is performedin the second rotary electric machine MG2. The fourth combination is setto the case where the overmodulation control is performed in the firstrotary electric machine MG1 and the normal modulation control isperformed in the second rotary electric machine MG2.

Then, as shown in a next equation, about each combination, the voltagecommand calculation unit 803 calculates a 2nd-order total coefficientα_all that totals the 2nd-order coefficients of corresponding respectivepower loss characteristics, calculates a 1st-order total coefficientβ_all that totals the 1st-order coefficients of respective power losscharacteristics, and calculates a 0-order total coefficient γ_all thattotals the 0-order coefficients of respective power losscharacteristics. Specifically, about the first combination, the voltagecommand calculation unit 803, for each order, totals the coefficient ofthe power loss characteristics of the normal modulation control of thefirst rotary electric machine MG1, the coefficient of the power losscharacteristics of the normal modulation control of the second rotaryelectric machine MG2, and the coefficient of the power losscharacteristics of the converter. About the second combination, thevoltage command calculation unit 803, for each order, totals thecoefficient of the power loss characteristics of the overmodulationcontrol of the first rotary electric machine MG1, the coefficient of thepower loss characteristics of the overmodulation control of the secondrotary electric machine MG2, and the coefficient of the power losscharacteristics of the converter. About the third combination, thevoltage command calculation unit 803, for each order, totals thecoefficient of the power loss characteristics of the normal modulationcontrol of the first rotary electric machine MG1, the coefficient of thepower loss characteristics of the overmodulation control of the secondrotary electric machine MG2, and the coefficient of the power losscharacteristics of the converter. About the fourth combination, thevoltage command calculation unit 803, for each order, totals thecoefficient of the power loss characteristics of the overmodulationcontrol of the first rotary electric machine MG1, the coefficient of thepower loss characteristics of the normal modulation control of thesecond rotary electric machine MG2, and the coefficient of the powerloss characteristics of the converter.

1) First Combination

MG1: Normal modulation control, MG2: Normal modulation controlα_all_1=α_mg1_1+α_mg2_1+α_dcdcβ_all_1=β_mg1_1+β_mg2_1+β_dcdcγ_all_1=γ_mg1_1+γ_mg2_1+γ_dcdc2) Second CombinationMG1: Overmodulation control, MG2: Overmodulation controlα_all_2=α_mg1_2+α_mg2_2+α_dcdcβ_all_2=β_mg1_2+β_mg2_2+β_dcdcγ_all_2=γ_mg1_2+γ_mg2_2+γ_dcdc3) Third combination . . . (9)MG1: Normal modulation control, MG2: Overmodulation controlα_all_3=α_mg1_1+α_mg2_2+α_dcdcβ_all_3=β_mg1_1+β_mg2_2+β_dcdcγ_all_3=γ_mg1_1+γ_mg2_2+γ_dcdc4) Fourth combinationMG1: Overmodulation control, MG2: Normal modulation controlα_all_4=α_mg1_2+α_mg2_1+α_dcdcβ_all_4=β_mg1_2+β_mg2_1+β_dcdcγ_all_4=γ_mg1_2+γ_mg2_1+γ_dcdc

Then, about each combination, the voltage command calculation unit 803calculates a total loss minimum voltage VHF which is the system voltagethat the sum total power loss becomes the minimum, based on the eachorder total coefficient α_all, β_all, and γ_all.

In the present embodiment, since the 2nd-order total coefficient α_allof each combination becomes a positive value, the sum total power lossbecomes a downwardly projected. Then, if voltage limitation describedbelow is not performed, the sum total power loss becomes the minimum atthe extremum. As shown in a next equation, about each combination, thevoltage command calculation unit 803 calculates an extremum of the2nd-order polynomial, based on the 2nd-order total coefficient α_all andthe 1st-order total coefficient β_all, and calculates the extremum asthe total loss minimum voltage VHP.VHP_1=−β_all_1/(2×α_all_1)VHP_2=−β_all_2/(2×α_all_2)  (10)VHP_3=−β_all_3/(2×α_all_3)VHP_4=−β_all_4/(2×α_all_4)

According to this configuration, without calculating the sum total powerloss at each operating point of the system voltage VH, the total lossminimum voltage VHP can be calculated by the extremum of the 2nd-orderpolynomial, and computation load can be reduced significantly.

If the 2nd-order total coefficient α_all becomes a negative value, or ifthe 3rd-order or higher, or 1st-order polynomial is used, about eachcombination, instead of the extremum of the 2nd-order polynomial, thevoltage command calculation unit 803 may calculate the system voltage VHthat the sum total power loss becomes the minimum in the voltage rangefrom the power source voltage Vb to the output upper limit voltageVcnmax of the converter, and may set it as the total loss minimumvoltage VHP.

<Determination of Executable Combination>

The voltage command calculation unit 803 determines whether or not eachcombination can be performed, based on the power source voltage Vb, theoutput upper limit voltage Vcnmax of the converter, the first bordervoltage Vmg1, and the second border voltage Vmg2.

Specifically, as shown in a next equation, when both of the first bordervoltage Vmg1 and the second border voltage Vmg2 is less than or equal tothe output upper limit voltage Vcnmax of the converter, the voltagecommand calculation unit 803 determines that the first combination (MG1:normal modulation control, MG2: normal modulation control) can beperformed; and otherwise, the voltage command calculation unit 803determines that the first combination cannot be performed.

1) When Vmg<=Vcnmax, and Vmg2<=Vcnmax

First combination is executable

2) Otherwise . . . (11)

First combination is unexecutable

As shown in a next equation, when both of the first border voltage Vmg1and the second border voltage Vmg2 is larger than the power sourcevoltage Vb, the voltage command calculation unit 803 determines that thesecond combination (MG1: overmodulation control, MG2: overmodulationcontrol) can be performed; and otherwise, the voltage commandcalculation unit 803 determines that the second combination cannot beperformed.

1) When Vb<Vmg1, and Vb<Vmg2

Second combination is executable

2) Otherwise . . . (12)

Second combination is unexecutable

As shown in a next equation, when the first border voltage Vmg1 is lessthan or equal to the output upper limit voltage Vcnmax of the converter,the second border voltage Vmg2 is larger than the power source voltageVb, and the first border voltage Vmg1 is smaller than the second bordervoltage Vmg2, the voltage command calculation unit 803 determines thatthe third combination (MG1: normal modulation control, MG2:overmodulation control) can be performed; and otherwise, the voltagecommand calculation unit 803 determines that the third combinationcannot be performed.

1) When Vmg1<=Vcnmax, Vb<Vmg2, and Vmg1<Vmg2

Third combination is executable

2) Otherwise . . . (13)

Third combination is unexecutable

As shown in a next equation, when the first border voltage Vmg1 islarger than the power source voltage Vb, the second border voltage Vmg2is less than or equal to the output upper limit voltage Vcnmax of theconverter, and the second border voltage Vmg2 is smaller than the firstborder voltage Vmg1, the voltage command calculation unit 803 determinesthat the fourth combination (MG1: overmodulation control, MG2: normalmodulation control) can be performed; and otherwise, the voltage commandcalculation unit 803 determines that the fourth combination cannot beperformed.

1) When Vb<Vmg1, Vmg2<=Vcnmax, and Vmg2<Vmg1

Fourth combination is executable

2) Otherwise . . . (14)

Fourth combination is unexecutable

Since the third combination is required to establish Vmg1<Vmg2, and thefourth combination is required to establish Vmg2<Vmg1, either one of thethird combination and the fourth combination can be performed.

<Calculation of Candidate Value and Minimum Sum Total Power Loss ofExecutable Each Combination>

About each combination determined as executable, the voltage commandcalculation unit 803 calculates the minimum value Ploss_min of sum totalpower loss, and the candidate value VHtp of the converter voltagecommand value, based on the total value of each order coefficient.

In the case where the first combination can be performed, as shown in anext equation and FIG. 16, when the total loss minimum voltage VHP_1 ofthe first combination is greater than or equal to the maximum valueVMAX1 among the first border voltage Vmg1, the second border voltageVmg2, and the power source voltage Vb, and is less than or equal to theoutput upper limit voltage Vcnmax of the converter, since the sum totalpower loss becomes the minimum at the total loss minimum voltage VHP_1of the first combination, the voltage command calculation unit 803 setsthe total loss minimum voltage VHP_1 of the first combination, as thecandidate value VHtp_1 of the converter voltage command value of thefirst combination. When the total loss minimum voltage VHP_1 of thefirst combination is smaller than the maximum value VMAX1, since the sumtotal power loss becomes the minimum at the maximum value VMAX1, thevoltage command calculation unit 803 sets the maximum value VMAX1, asthe candidate value VHtp_1 of the converter voltage command value of thefirst combination. When the total loss minimum voltage VHP_1 of thefirst combination is larger than the output tipper limit voltage Vcnmaxof the converter, since the sum total power loss becomes the minimum atthe output upper limit voltage Vcnmax of the converter, the voltagecommand calculation unit 803 sets the output upper limit voltage Vcnmax,as the candidate value VHtp_1 of the converter voltage command value ofthe first combination. Here, MAX (A, B, C) is a function which outputsthe largest value among A, B, and C.VMAX1−MAX(Vmg1,Vmg2,Vb)  (15)1) When VMAX1<=VHP_1<=VcnmaxVHtp_1=VHP_12) When VHP_1<VMAX1VHtp_1=VMAX13) When Vcnmax<VHP_1VHtp_1=Vcnmax

If the 2nd-order total coefficient α_all_1 of the first combinationbecomes a negative value, or if the 3rd-order or higher, or 1st-orderpolynomial is used, the voltage command calculation unit 803 maycalculate the system voltage VH that the sum total power loss becomesthe minimum in a settable range of the candidate value VHtp_1 of thefirst combination (from VMAX1 to Vcnmax), as the candidate value VHtp_1of the first combination.

Then, as shown in a next equation, the voltage command calculation unit803 calculates the minimum sum total power loss Ploss_min_1 of the firstcombination at the calculated candidate value VHtp_1 of the convertervoltage command value of the first combination.Ploss_min_1=α_all_1·VHtp_1²+β_all_1·VHtp_1+γ_all_1  (16)

In the case where the second combination can be performed, as shown in anext equation and FIG. 17, when the total loss minimum voltage VHP_2 ofthe second combination is greater than or equal to the power sourcevoltage Vb, and is less than or equal to the minimum value VMIN2 amongthe first border voltage Vmg1, the second border voltage Vmg2, and theoutput upper limit voltage Vcnmax of the converter, since the sum totalpower loss becomes the minimum at the total loss minimum voltage VHP_2of the second combination, the voltage command calculation unit 803 setsthe total loss minimum voltage VHP_2 of the second combination, as thecandidate value VHtp_2 of the converter voltage command value of thesecond combination. When the total loss minimum voltage VHP_2 of thesecond combination is larger than the minimum value VMIN2, since the sumtotal power loss becomes the minimum at the minimum value VMIN2, thevoltage command calculation unit 803 sets the minimum value VMIN2, asthe candidate value VHtp_2 of the converter voltage command value of thesecond combination. When the total loss minimum voltage VHP_2 of thesecond combination is smaller than the power source voltage Vb, sincethe sum total power loss becomes the minimum at the power source voltageVb, the voltage command calculation unit 803 sets the power sourcevoltage Vb, as the candidate value VHtp_2 of the converter voltagecommand value of the second combination. Here, MIN (A, B, C) is afunction which outputs the smallest value among A, B, and C.VMIN2−MIN(Vmg1,Vmg2,Vcnmax)  (17)1) When Vb<=VHP_2<=VMIN2VHtp_2=VHP_22) When VMIN2<VHP_2VHtp_2=VMIN23) When VHP_2<VbVHtp_2=Vb

If the 2nd-order total coefficient α_all_2 of the second combinationbecomes a negative value, or if the 3rd-order or higher, or 1st-orderpolynomial is used, the voltage command calculation unit 803 maycalculate the system voltage VH that the sum total power loss becomesthe minimum in a settable range of the candidate value VHtp_2 of thesecond combination (from Vb to VMIN2), as the candidate value VHtp_2 ofthe second combination.

Then, as shown in a next equation, the voltage command calculation unit803 calculates the minimum sum total power loss Ploss_min_2 of thesecond combination at the calculated candidate value VHtp_2 of theconverter voltage command value of the second combination.Ploss_min_2=α_all_2·VHtp_2²+β_all_2·VHtp_2+γ_all_2  (18)

In the case where the third combination can be performed, as shown in anext equation and FIG. 18, when the total loss minimum voltage VHP_3 ofthe third combination is the greater than or equal to the maximum valuesVMAX3 between the first border voltage Vmg1 and the power source voltageVb, and is less than or equal to the minimum value VMIN3 between thesecond border voltage Vmg2 and the output upper limit voltage Vcnmax ofthe converter, since the sum total power loss becomes the minimum at thetotal loss minimum voltage VHP_3 of the third combination, the voltagecommand calculation unit 803 sets the total loss minimum voltage VHP_3of the third combination, as the candidate value VHtp_3 of the convertervoltage command value of the third combination. When the total lossminimum voltage VHP_3 of the third combination is smaller than themaximum value VMAX3, since the sum total power loss becomes the minimumat the maximum value VMAX3, the voltage command calculation unit 803sets the maximum value VMAX3, as the candidate value VHtp_3 of theconverter voltage command value of the third combination. When the totalloss minimum voltage VHP_3 of the third combination is larger than theminimum value VMIN3, the voltage command calculation unit 803 sets theminimum value VMIN3, as the candidate value VHtp_3 of the convertervoltage command value of the third combination.VMAX3−MAX(Vmg1,Vb)  (19)VMIN3−MIN(Vmg2,Vcnmax)1) When VMAX3<=VHP_3<=VMIN3VHtp_3=VHP_32) When VHP_3<VMAX3VHtp_3=VMAX33) when VMIN3<VHP_3VHtp_3=VMIN3

If the 2nd-order total coefficient α_all_3 of the third combinationbecomes a negative value, or if the 3rd-order or higher, or 1st-orderpolynomial is used, the voltage command calculation unit 803 maycalculate the system voltage VH that the sum total power loss becomesthe minimum in a settable range of the candidate value VHtp_3 of thethird combination (from VMAX3 to VMIN 3), as the candidate value VHtp_3of the third combination.

Then, as shown in a next equation, the voltage command calculation unit803 calculates the minimum sum total power loss Ploss_pin_3 of the thirdcombination at the calculated candidate value VHtp_3 of the convertervoltage command value of the third combination.Ploss_min_3=α_all_3·VHtp·3²+β_all_3·VHtp_3+γ_all_3  (20)

In the case where the fourth combination can be performed, as shown in anext equation and FIG. 19, when total loss minimum voltage VHP_4 of thefourth combination is greater than or equal to the maximum values VMAX4between the second border voltage Vmg2 and the power source voltage Vb,and is less than or equal to the minimum value VMIN4 between the firstborder voltage Vmg1 and the output upper limit voltage Vcnmax of theconverter, since the sum total power loss becomes the minimum at thetotal loss minimum voltage VHP_4 of the fourth combination, the voltagecommand calculation unit 803 sets the total loss minimum voltage VHP_4of the fourth combination, as the candidate value VHtp_4 of theconverter voltage command value of the fourth combination. When thetotal loss minimum voltage VHP_4 of the fourth combination is smallerthan the maximum value VMAX4, since the sum total power loss becomes theminimum at the maximum value VMAX4, the voltage command calculation unit803 sets the maximum value VMAX4, as the candidate value VHtp_4 of theconverter voltage command value of the fourth combination. When thetotal loss minimum voltage VHP_4 of the fourth combination is largerthan the minimum value VMIN4, the voltage command calculation unit 803sets the minimum value VMIN4, as the candidate value VHtp_4 of theconverter voltage command value of the fourth combination.VMAX4=MAX(Vmg2,Vb)  (21)VMIN4=MIN(Vmg1,Vcnmax)1) When VMAX4<=VHP_4<=VMIN4VHtp_4=VHP_42) When VHP_4<VMAX4VHtp_4=VMAX43) When VMIN4<VHP_4VHtp_4=VMIN4

If the 2nd-order total coefficient α_all_4 of the fourth combinationbecomes a negative value, or if the 3rd-order or higher, or let-orderpolynomial is used, the voltage command calculation unit 803 maycalculate the system voltage VH that the sum total power loss becomesthe minimum in a settable range of the candidate value VHtp_4 of thefourth combination (from VMAX4 to VMIN4), as the candidate value VHtp_4of the fourth combination.

Then, as shown in a next equation, the voltage command calculation unit803 calculates the minimum sum total power loss Ploss_min_4 of thefourth combination at the calculated candidate value VHtp_4 of theconverter voltage command value of the fourth combination.Ploss_min_4=α_all_4·VHtp_4²+β_all_4·VHtp_4+γ_all_4  (22)

As shown in a next equation, the voltage command calculation unit 803determines the minimum value Ploss_minall among the minimum sum totalpower losses Ploss_min_1, Ploss_min_2, Ploss_min_3, and Ploss_min_4 ofexecutable the first combination to the fourth combination, and sets thecandidate value VHtp of the converter voltage command value of thecombination corresponding to the determined minimum value Ploss_minall,as the converter voltage command value VH #. Herein, as mentioned above,since the fourth combination and the third combination can be performedalternatively, any one of the minimum sum total power loss Ploss_min isused. For example, if the minimum sum total power loss Ploss_min_1 ofthe first combination becomes the minimum value, the candidate valueVHtp_1 of the converter voltage command value of the first combinationis set as the converter voltage command value VH #.Ploss_minall=MIN(Ploss_min_1,Ploss_min_2,Ploss_min_3 or Ploss_min_4)VH #=VHtp of combination corresponding to Ploss_minall   (23)<Consideration of Loss Due to Command Value Change>

The voltage command calculation unit 803 calculates a changing powerloss LossMove due to changing from the converter voltage command valueVH # which is set in the last time calculation cycle into the convertervoltage command value VH # which is calculated by the equation (23) inthis time calculation cycle; and calculates a maintaining power lossLossCur due to maintaining to the converter voltage command value VH #which is set in the last time calculation cycle. Then, when themaintaining power loss LossCur exceeds the changing power loss LossMove,the voltage command calculation unit 803 sets the converter voltagecommand value VH # calculated in this time calculation cycle, as thefinal setting value. On the other hand, when the maintaining power lossLossCur is below the changing power loss LossMove, the voltage commandcalculation unit 803 sets the converter voltage command value VH # whichis set in the last time calculation cycle, as the final setting value.

<Example of Conversion>

There has been explained the case where the converter voltage commandcalculation unit 700 calculates the power loss characteristics(coefficients of polynomial) of total of the rotary electric machine andthe inverter. However, the converter voltage command calculation unit700 may calculates the power loss characteristics (coefficients ofpolynomial) of the rotary electric machine, and the power losscharacteristics (coefficients of polynomial) of the inverter,respectively, and may total two calculated power loss characteristics(coefficients of polynomial).

If the power loss characteristics of the rotary electric machine isunknown, the converter voltage command calculation unit 700 maycalculate the power loss characteristics (coefficients of polynomial) ofonly the inverter. Even in this case, since the increase in theswitching loss and the energization loss in the magnetic flux weakeningcontrol can be expressed, the converter voltage command value VH # whichmakes the power loss the minimum can be calculated with good accuracygenerally. If the power loss characteristics of the converter isunknown, the converter voltage command calculation unit 700 maycalculate the power loss characteristics of the rotary electric machineand the inverter, or the power loss characteristics of the inverter,without calculating the power loss characteristics of the converter.

There has been explained the case where the 2nd-order polynomial is usedabout each power loss characteristics. However, the 1st-orderpolynomial, or the 3rd-order or higher-order polynomial may be usedabout each power loss characteristics. Even in this case, about eachcombination, the existing coefficients of each order are totaled. Inthis case, as mentioned above, about each combination, instead of theextremum of the 2nd-order polynomial, the system voltage VH that the sumtotal power loss becomes the minimum in the voltage range from the powersource voltage Vb to the output upper limit voltage Vcnmax of theconverter may be calculated based on the total coefficient of eachorder, and it may be set as the total loss minimum voltage VHP.

2. Embodiment 2

The controller 400 according to Embodiment 2 will be explained. Theexplanation for constituent parts the same as those in Embodiment 1 willbe omitted. The basic configuration of the controller 400 according tothe present embodiment is the same as that of Embodiment 1. Calculationprocessing of the converter voltage command calculation unit 700 isdifferent from Embodiment 1.

Depending on inductance and constant of the capacitor used for theconverter 15, and the operating point of the rotary electric machine,when the system voltage VH which becomes the output voltage of theconverter 15 is close to the power source voltage Vb, the system voltageVH may oscillate.

Then, in the present embodiment, the converter voltage commandcalculation unit 700 set any larger one of the converter voltage commandvalue VH # which is calculated in Embodiment 1 and makes the power lossthe minimum, and an avoidance minimum voltage VHav which is a minimumsystem voltage required for avoiding instability of the rotary electricmachine apparatus, as the final converter voltage command value VH #.The converter voltage command calculation unit 700 calculates theavoidance minimum voltage VHav, based on the operating points of therotary electric machine (the torque command value Tqcom and therotational angle speed ω of each rotary electric machine, the totaloutput PMOT_ALL of two rotary electric machines, and the like). Forexample, the avoidance minimum voltage VHav is calculated by adding thevoltage width ΔVth for avoiding oscillation to the power source voltageVb.

According to this configuration, while reducing power loss, oscillationof the system voltage VH can be suppressed.

3. Embodiment 3

The controller 400 according to Embodiment 3 will be explained. Theexplanation for constituent parts the same as those in Embodiment 1 willbe omitted. The basic configuration of the controller 400 according tothe present embodiment is the same as that of Embodiment 1. Calculationprocessing of the converter voltage command calculation unit 700 isdifferent from Embodiment 1.

When the field weakening control is performed in one or both of thefirst and the second rotary electric machines MG1, MG2, thedirect-current side current of each inverter may oscillate easily.Therefore, in the case where the field weakening control is performed,as similar to Embodiment 2, when the system voltage VH is close to thepower source voltage Vb, the system voltage VH may oscillate.

Then, in the present embodiment, the converter voltage commandcalculation unit 700 sets any larger one of the converter voltagecommand value VH # which is calculated in Embodiment 1 when the invertercontrol unit 600 calculates the three-phase voltage command values forperforming the field weakening control and makes the power loss theminimum, and the avoidance minimum voltage VHav which is a minimumsystem voltage required for avoiding instability of the rotary electricmachine apparatus, as the final converter voltage command value VH #. Assimilar to Embodiment 2, the converter voltage command calculation unit700 calculates the avoidance minimum voltage VHav, based on theoperating points of the rotary electric machine (the torque commandvalue Tqcom and the rotational angle speed ω of each rotary electricmachine, the total output PMOT_ALL of two rotary electric machines, andthe like). For example, the avoidance minimum voltage VHav is calculatedby adding the voltage width ΔVth for avoiding oscillation to the powersource voltage Vb.

According to this configuration, while reducing power loss, oscillationof the system voltage VH due to execution of the field weakening controlcan be suppressed.

Other Embodiments

(1) In each of above embodiments, there has been explained the casewhere 2 sets of the rotary electric machine MG and the inverter IN areprovided, and the controller 400 is configured in accordance with thefirst set and the second set. However, 1 set, 3 sets, or more than 3sets of the rotary electric machine MG and the inverter IN may beprovided. The controller 400 is appropriately configured in accordancewith the number of sets.

(2) In each of above embodiments, the approximate expression of thepower loss and the calculation example of the coefficients about theconverter 15, the inverter IN, and the rotary electric machine MG areonly representative ones. These can be calculated based on other methodsor other variables. Also in the case where the number of the converter15, the number of the inverter IN, and the number of the rotary electricmachine MG increase, these loss characteristics can be approximatedsimilarly, coefficients can be calculated similarly, and the convertervoltage command value VH # at which the power loss becomes the minimumcan be set.

(3) Limiting to a part of the power loss characteristics of theconverter, the power loss characteristics of the inverter, and the powerloss characteristics of the rotary electric machine, in which a changedegree with respect to change of the system voltage VH is large,coefficients when the power loss characteristics is approximated by thepolynomial may be calculated, and the converter voltage command value VH# at which the power loss characteristics becomes the minimum may be setbased on the calculated coefficients.

(4) In each of above embodiments, there has been explained the casewhere the rotary electric machine apparatus 1000 is mounted on thehybrid vehicle. However, the rotary electric machine apparatus 1000 maybe a driving force source of other apparatus other than the hybridvehicle, such as being mounted on the electric vehicle.

Although the present disclosure is described above in terms of variousexemplary embodiments and implementations, it should be understood thatthe various features, aspects and functionality described in one or moreof the individual embodiments are not limited in their applicability tothe particular embodiment with which they are described, but instead canbe applied, alone or in various combinations to one or more of theembodiments. It is therefore understood that numerous modificationswhich have not been exemplified can be devised without departing fromthe scope of the present application. For example, at least one of theconstituent components may be modified, added, or eliminated. At leastone of the constituent components mentioned in at least one of thepreferred embodiments may be selected and combined with the constituentcomponents mentioned in another preferred embodiment.

What is claimed is:
 1. A controller for rotary electric machineapparatus that controls a rotary electric machine apparatus which isprovided with a rotary electric machine which has plural-phase windings,a converter which can raise a power source voltage of a direct currentpower source to output to a system voltage line, and an inverter whichis provided between the converter and the rotary electric machine andperforms power conversion between the direct current power of the systemvoltage line and alternating current power which drives the rotaryelectric machine, the controller for rotary electric machine apparatuscomprising at least one processor configured to implement: a convertervoltage command calculator that calculates a converter voltage commandvalue within a range of greater than or equal to the power sourcevoltage and less than or equal to an output upper limit voltage of theconverter, a converter controller that controls the converter so that asystem voltage which is a direct current voltage of the system voltageline approaches the converter voltage command value, and an invertercontroller that calculates plural-phase voltage command values, andcontrols the inverter based on the plural-phase voltage command valuesto apply voltages to the plural-phase windings, wherein the invertercontroller switches and performs a normal modulation control in whichamplitudes of the plural-phase voltage command values become less thanor equal to a half value of the system voltage, and an overmodulationcontrol in which the amplitudes of the plural-phase voltage commandvalues exceed the half value of the system voltage, and wherein theconverter voltage command calculator sets the system voltage that apower loss becomes a minimum, as the converter voltage command value,based on a power loss characteristics of the normal modulation controlwhich is a power loss characteristics of at least the inverter withrespect to the system voltage in performing the normal modulationcontrol, and a power loss characteristics of the overmodulation controlwhich is a power lose characteristics of at least the inverter withrespect to the system voltage in performing the overmodulation control.2. The controller for rotary electric machine apparatus according toclaim 1, wherein the converter voltage command calculator calculates aminimum value of the power loss in performing the normal modulationcontrol, and the system voltage at the calculated minimum value of thepower loss, based on the power loss characteristics of the normalmodulation control; calculates a minimum value of the power loss inperforming the overmodulation control, and the system voltage at thecalculated minimum value of the power loss, based on the power losscharacteristics of the overmodulation control; and determines anysmaller one of the minimum value of the power loss in performing thenormal modulation control and the minimum value of the power loss inperforming the overmodulation control, and sets the system voltage atthe determined smaller one, as the converter voltage command value. 3.The controller for rotary electric machine apparatus according to claim1, wherein the converter voltage command calculator sets the systemvoltage that a sum total power loss of the inverter, the rotary electricmachine, and the converter becomes a minimum, as the converter voltagecommand value, based on the power loss characteristics of the normalmodulation control which is a power loss characteristics of the inverterand the rotary electric machine with respect to the system voltage inperforming the normal modulation control, the power loss characteristicsof the overmodulation control which is a power loss characteristics ofthe inverter and the rotary electric machine with respect to the systemvoltage in performing the overmodulation control, and a power losscharacteristics of the converter with respect to the system voltage. 4.The controller for rotary electric machine apparatus according to claim1, wherein the converter voltage command calculator sets the systemvoltage that a sum total power loss of the inverter and the converterbecomes a minimum, as the converter voltage command value, based on thepower loss characteristics of the normal modulation control which is apower loss characteristics of the inverter with respect to the systemvoltage in performing the normal modulation control, the power losscharacteristics of the overmodulation control which is a power losscharacteristics of the inverter with respect to the system voltage inperforming the overmodulation control, and a power loss characteristicsof the converter with respect to the system voltage.
 5. The controllerfor rotary electric machine apparatus according to claim 1, wherein theconverter voltage command calculator calculates coefficients ofrespective orders of a polynomial which represents each power losscharacteristics and uses the system voltage as a variable.
 6. Thecontroller for rotary electric machine apparatus according to claim 5,wherein the polynomial is a polynomial whose order is smaller than orequal to the 2nd-order.
 7. The controller for rotary electric machineapparatus according to claim 1, wherein a plurality of sets of therotary electric machine and the inverter are provided, and wherein theconverter voltage command calculator sets the system voltage that apower loss obtained by totaling a plurality of sets becomes a minimum,as the converter voltage command value, based on each set of the powerloss characteristics of the normal modulation control and the power losscharacteristics of the overmodulation control.
 8. The controller forrotary electric machine apparatus according to claim 7, wherein theconverter voltage command calculator, about each of a plurality ofcombinations which combined the case where the normal modulation controlor the overmodulation control is performed in each set, calculates aminimum value of power loss and calculates the system voltage at thecalculated minimum value as a candidate value of the converter voltagecommand value, based on each set of the power loss characteristics ofthe normal modulation control or the power loss characteristics of theovermodulation control; and determines the combination that the minimumvalue of the power lose becomes the smallest in the plurality ofcombinations, and sets the candidate value of the converter voltagecommand value in the determined combination, as the converter voltagecommand value.
 9. The controller for rotary electric machine apparatusaccording to claim 8, wherein the converter voltage command calculatorcalculates coefficients of respective orders of a polynomial whichrepresents each power loss characteristics and uses the system voltageas a variable; and about each of the plurality of combinations, totalsthe coefficients of corresponding respective power loss characteristicsfor each order of the polynomials, and calculates the minimum value ofpower loss and the candidate value of the converter voltage commandvalue, based on the total value of the coefficients of each order. 10.The controller for rotary electric machine apparatus according to claim8, wherein the converter voltage command calculator, about each set,calculates a border voltage which is the minimum system voltage requiredin the case of performing the normal modulation control; determineswhether or not each combination can be performed, based on the powersource voltage, an output upper limit voltage of the converter, and theborder voltage of each set; and about each combination determined asexecutable, calculates the minimum value of power loss and the candidatevalue of the converter voltage command value, based on the total valueof the coefficients of each order.
 11. The controller for rotaryelectric machine apparatus according to claim 1, wherein the convertervoltage command calculator sets any larger one of the system voltagethat a power loss becomes a minimum and the minimum system voltagerequired for avoiding instability of the rotary electric machineapparatus, as the converter voltage command value.
 12. The controllerfor rotary electric machine apparatus according to claim 1, wherein whenthe inverter controller calculates the plural-phase voltage commandvalues for performing a field weakening control, the converter voltagecommand calculator sets any larger one of the system voltage that apower loss becomes a minimum, and the minimum system voltage requiredfor avoiding instability of the rotary electric machine apparatus, asthe converter voltage command value.